The abnormal ECG and myocardial pathology produced by the behavior stress of Sidman avoidance behavior and cardiac rate conditioning will be studied in squirrel monkeys and rats. With various experimental procedures, the psychological and physiological environment will be manipulated, and the effects of cardiovascular function and pathology evaluated. Thus, the specific factors in a stressful environment which cause these functional and pathologic disturbances of the cardiovascular system will be elucidated. Since these changes in cardiac function and pathology are strikingly similar to those observed in human cardiovascular dysfunction resulting from central nervous system pathology. This research analogue affords an unique opportunity to explore new techniques which may have therapeutic value, but cannot be easily evaluated in human experiments. Therefore, these experiments will contribute not only to a better understanding of the mechanisms that contribute to cardiovascular pathology but also provide information that may be helpful for treatment of clinical disorders.